Journal articles: 'Hard-acceleration'

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Su, Jie, Zhenghua Zhou, You Zhou, Xiaojun Li, Qing Dong, Yafei Wang, Yuping Li, and Liu Chen. "The Characteristics of Seismic Response on Hard Interlayer Sites." Advances in Civil Engineering 2020 (June 25, 2020): 1–11. http://dx.doi.org/10.1155/2020/1425969.

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Based on the engineering geological data of a nuclear power plant site, nine engineering geological profiles were created with hard interlayers of different thicknesses. The equivalent linearization method of seismic motion segment-input used for one-dimensional nonlinear seismic response analysis was applied to study the effect of the interlayer thickness on the peak acceleration and the acceleration response spectra of the site seismic response. The results showed that there was an obvious influence of hard interlayer thickness on site seismic responses. With the increase of hard interlayer thickness, the site nonlinear effect on seismic responses decreased. Under the same thickness of the hard interlayer, the nonlinear effect of the site was strengthened with the higher input peak acceleration. In addition, the short-period acceleration response spectrum was found to be significantly influenced by the hard interlayer and showed that the longer the period, the less influence of the hard interlayer on the acceleration response spectrum coordinates. Moreover, the influenced frequency band was wider with the increase in the thickness of hard interlayer.

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Hao, Hui Yan, Ya Bin Wang, Ming Jie Liu, and Xiao Feng Li. "Penetration Acceleration Signal Overload Rigid Separation Base on Local Mean Decomposition." Applied Mechanics and Materials 128-129 (October 2011): 938–41. http://dx.doi.org/10.4028/www.scientific.net/amm.128-129.938.

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Hard target penetration acceleration signals are non-stationary signals. In this paper use the local mean decomposition theory to analysis hard target penetration acceleration signals. Local mean decomposition can adaptively decompose any complex non-stationary signal into a number of physically meaningful instantaneous frequency components and these components could well reflect the intrinsic nature of the signals. Use local mean decomposition to separate the rigid projectile overload from hard target penetration acceleration signals. That provide reliable data to support accurately calculating the effective penetration depth, hard floors or holes through the number of target parameters on the penetration of weapons is significant. The author apply local mean decomposition algorithm in penetration acceleration signal separation and the results verify the effectiveness of the method.

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Masuda, S., and J. Sato. "Hard X-ray footpoint motion and acceleration mechanism." Advances in Space Research 32, no. 12 (January 2003): 2455–58. http://dx.doi.org/10.1016/j.asr.2003.03.003.

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Tian, Shuxia, Penghui Zhang, Liping Huang, Xueqian Song, Zhenmao Chen, Jianxiu Liu, Wenbin He, and Yang Cao. "Hard-point detection of catenary based on Hidden Markov Model." International Journal of Applied Electromagnetics and Mechanics 64, no. 1-4 (December 10, 2020): 701–9. http://dx.doi.org/10.3233/jae-209381.

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Hard-point detection is an important content of catenary detection. In this paper, the pantograph-catenary coupling model was established firstly. Then the vertical acceleration of pantograph during operation was calculated by using three-dimensional modeling software and finite element analysis software. The acceleration signal mixed with white noise was filtered by global default threshold, and the hard-point detection feature signal was obtained. Finally, the Hidden Markov Model corresponding to each state of the hard-point was obtained by using the characteristic signal, which verified the feasibility of the Hidden Markov Model for hard-point detection.

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Asano, Katsuaki, and Masaaki Hayashida. "Blazar Spectra with Hard-sphere-like Acceleration of Electrons." Astrophysical Journal 861, no. 1 (June 28, 2018): 31. http://dx.doi.org/10.3847/1538-4357/aac82a.

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Koylu, Hakan, and Ali Cinar. "Development of control algorithm for ABS–suspension integration to reduce rotational acceleration oscillations of wheel." Transactions of the Institute of Measurement and Control 40, no. 3 (November 13, 2016): 1018–34. http://dx.doi.org/10.1177/0142331216677318.

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In this study, we aimed to obtain smoother wheel rotational acceleration during braking with an activated anti-lock brake system (ABS). This produces effective and easily controlled rotational acceleration of a wheel by an ABS control unit. For this, the wheel load is changed by considering the interaction between the brake pressure change rates and rotational acceleration of the wheel. This is provided by means of the control strategy developed in this study. The rules of the control strategy are based on ABS test results. These tests are conducted with soft, medium-hard and hard dampers on wet and slippery road surfaces. Therefore, the control strategy changes the wheel load by setting the damper stage according to agreement between brake pressure and wheel rotational acceleration. Here, the control strategy constantly applies the damping force of the damper providing the shortest braking distance under wet or slippery road conditions. All results show that the control strategy considerably improves wheel rotational acceleration oscillations during braking with an activated ABS.

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CROMARTY, S. I., J. S. COBB, and G. KASS-SIMON. "Behavioral Analysis of the Escape Response in the Juvenile Lobster Homarus Americanus Over the Molt Cycle." Journal of Experimental Biology 158, no. 1 (July 1, 1991): 565–81. http://dx.doi.org/10.1242/jeb.158.1.565.

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1. Components of the escape response of the American lobster were compared over the molt cycle. Number of tailflips, frequency, duration and distance were measured. Velocity, acceleration, force and work were computed from the above measurements, using time-lapse video-recordings of escaping lobsters. 2. Soft-shelled postmolt lobsters (stage B) traveled further, spent more time tailflipping and performed a larger number of tailflips than hard-shelled premolt lobsters (stage D). Hard-shelled lobsters had a more forceful initial power swim, achieved a higher overall velocity and acceleration and, therefore, produced more forceful swims with greater energy expenditure (measured by work output) than soft-shelled animals. 3. Among hard-shelled lobsters, velocity, acceleration, force and work fell off markedly in the latter part of their subsequent swims as a consequence of the prolonged duration and reduced frequency of these swims. Soft-shelled lobsters sustained their swimming velocity, acceleration, force and work for their entire subsequent swimming response. 4. There are likely to be large molt-related differences in energy metabolism, endocrinology and nerve and muscle physiology which lead to the observed differences in the escape response.

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Jinzenji, A., T. Sasamoto, K. Aikawa, S. Yoshida, and K. Aruga. "Acceleration feedforward control against rotational disturbance in hard disk drives." IEEE Transactions on Magnetics 37, no. 2 (March 2001): 888–93. http://dx.doi.org/10.1109/20.917637.

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Burdzy, Krzysztof, Mauricio Duarte, Carl-Erik Gauthier, C. Robin Graham, and Jaime San Martin. "Fermi acceleration in rotating drums." Journal of Mathematical Physics 63, no. 6 (June 1, 2022): 062706. http://dx.doi.org/10.1063/5.0082981.

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Consider hard balls in a bounded rotating drum. If there is no gravitation, then there is no Fermi acceleration, i.e., the energy of the balls remains bounded forever. If there is gravitation, Fermi acceleration may arise. A number of explicit formulas for the system without gravitation are given. Some of these are based on an explicit realization, which we derive, of the well-known microcanonical ensemble measure.

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Benz, Arnold O., Paolo C. Grigis, and Marco Battaglia. "Electron acceleration in solar flares: observations versus numerical simulations." Proceedings of the International Astronomical Union 2, no. 14 (August 2006): 87. http://dx.doi.org/10.1017/s1743921307009908.

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Murugan, N., C. Sagong, A. S. Cuamatzi Castelan, K. Moss, T. Roth, C. L. Drake, and P. Cheng. "0203 To and From the Night Shift: Risky On-the-Road Driving in Night Shift Workers." Sleep 43, Supplement_1 (April 2020): A79—A80. http://dx.doi.org/10.1093/sleep/zsaa056.201.

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Abstract Introduction Drowsy driving is a common occupational hazard for night shift workers (NSWs). While sleep loss is commonly identified as the primary culprit of drowsy driving, another critical factor to consider is circadian phase. However, the role of circadian phase in driving safety has not been well characterized in NSWs. This study examined if dim light melatonin offset (DLMOff, i.e. the cessation of melatonin secretion) is also a relevant phase marker of susceptibility to four different subtypes of risky on-the-road driving behaviors. Methods On-the-road driving was monitored over 8 weeks via a mobile application that tracked risky driving behaviors using accelerometer and GPS data from cell phones (N=15; 3052 total driving events recorded). Risky driving behaviors included: 1) frequency of hard-braking events, 2) frequency of aggressive-acceleration events, 3) duration of excessive-speeding, and 4) duration of phone-usage. At week 2, participants spent 24 hours in-lab where hourly saliva samples were collected and assayed for melatonin, and DLMOff was calculated. Phase angle of driving events relative to DLMOff was used as the predictor in nested mixed-effects regressions, with risky driving behaviors as the outcome variables. Results The most common occurrences of risky driving were phone-usage and hard-braking. On average, NSWs had 46.7% and 42.0% of driving events with at least one occurrence of phone-usage and hard-braking, respectively. Rates of aggressive-acceleration and speeding were 24.4% and 20.4%. Positive phase angles (i.e. driving after DLMOff) were associated with reduced rates of hard-braking and aggressive-acceleration, but not of phone-usage and excessive-speeding. Specifically, rates of hard-braking and aggressive-acceleration decreased by 4.5% (p<.01) and 3.4% (p=.05) every two hours following DLMOff, respectively. Conclusion The study suggests DLMOff appears to be an important variable for predicting accident risk in NSWs. If replicated, circadian phase should be considered in recommendations to increase occupational health and safety of NSWs. Support Support for this study was provided to PC by NHLBI (K23HL138166).

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Arad, Ofir, Assaf Lavi, and Uri Keshet. "Maximally hard radio spectra from Fermi acceleration in pulsar-wind nebulae." Monthly Notices of the Royal Astronomical Society 504, no. 4 (April 15, 2021): 4952–67. http://dx.doi.org/10.1093/mnras/stab1044.

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ABSTRACT The processes leading to the exceptionally hard radio spectra of pulsar-wind nebulae (PWNe) are not yet understood. Radio photon spectral indices among 29 PWNe from the literature show an approximately normal, α = 0.2 ± 0.2 distribution. We present ∼3σ evidence for a distinct sub-population of PWNe, with a hard spectrum α = 0.01 ± 0.06 near the termination shock and significantly softer elsewhere, possibly due to a recent evacuation of the shock surroundings. Such spectra, especially in the hard sub-population, suggest a Fermi process, such as diffusive shock acceleration (DSA), at its extreme, α = 0 limit. In particular, we show that this limit is approached in DSA for sufficiently anisotropic small-angle scattering, enhanced on either side of the shock for particles approaching the shock front. In the upstream, the spectral hardening is mostly associated with an enhanced energy gain, possibly driven by the same beamed particles crossing the shock. Downstream, the main effect is a diminished escape probability, but this lowers the acceleration efficiency to $\lesssim 25{{\ \rm per\ cent}}$ for α = 0.3 and $\lesssim 1{{\ \rm per\ cent}}$ for α = 0.03.

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Zhang, Tian-Xi, Arjun Tan, and Shi Tsan Wu. "Solar Impulsive Hard X-Ray Emission and Two-Stage Electron Acceleration." Chinese Journal of Astronomy and Astrophysics 6, no. 6 (October 2006): 733–40. http://dx.doi.org/10.1088/1009-9271/6/6/13.

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Lin, R. P. "Particle Acceleration by the Sun: Electrons, Hard X-rays/Gamma-rays." Space Science Reviews 124, no. 1-4 (January 30, 2007): 233–48. http://dx.doi.org/10.1007/s11214-006-9107-9.

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Hu, Yun, and Hegang Li. "Biological mechanism of surgery-mediated acceleration of orthodontic tooth movement: A narrative review." Journal of International Medical Research 50, no. 9 (September 2022): 030006052211239. http://dx.doi.org/10.1177/03000605221123904.

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Surgery-mediated acceleration of orthodontic tooth movement (SAOTM) has been proven effective for decades. Research has confirmed that surgical approaches play an important role in adult patients with a short orthodontic treatment time. The mechanism of SAOTM involves short-term acceleration of localized hard and soft tissue remodeling, known as the regional acceleratory phenomenon. However, no relevant review on the biological mechanism of SAOTM has been performed to date. The proposed biological mechanism of acceleration of OTM involves the participation of various cells, cytokines, and signaling pathways. We herein review the relevant literature and summarize the biological mechanism of SAOTM to provide new insights for further research on acceleration of OTM.

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Li, Xiaocan, Fan Guo, Bin Chen, Chengcai Shen, and Lindsay Glesener. "Modeling Electron Acceleration and Transport in the Early Impulsive Phase of the 2017 September 10th Solar Flare." Astrophysical Journal 932, no. 2 (June 1, 2022): 92. http://dx.doi.org/10.3847/1538-4357/ac6efe.

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Abstract The X8.2-class limb flare on 2017 September 10 is among the best studied solar flare events owing to its great similarity to the standard flare model and the broad coverage by multiple spacecraft and ground-based observations. These multiwavelength observations indicate that electron acceleration and transport are efficient in the reconnection and flare looptop regions. However, there lacks a comprehensive model for explaining and interpreting the multi-faceted observations. In this work, we model the electron acceleration and transport in the early impulsive phase of this flare. We solve the Parker transport equation that includes the primary acceleration mechanism during magnetic reconnection in the large-scale flare region modeled by MHD simulations. We find that electrons are accelerated up to several MeV and fill a large volume of the reconnection region, similar to the observations shown in microwaves. The electron spatial distribution and spectral shape in the looptop region agree well with those derived from the microwave and hard X-ray emissions before magnetic islands grow large and dominate the acceleration. Future emission modelings using the electron maps will enable direct comparison with microwave and hard X-ray observations. These results shed new light on the electron acceleration and transport in a broad region of solar flares within a data-constrained realistic flare geometry.

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Melrose, D. B. "The Nature of Flat Spectrum Sources." Symposium - International Astronomical Union 175 (1996): 423–26. http://dx.doi.org/10.1017/s0074180900081328.

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Nonthermal radio sources near the Galactic Center with flat or weakly inverted spectra (S((ω) ∝ ωα with α ≳ 0) are attributed to optically thin synchrotron emission from a hard electron energy spectrum, N(ε) ∝ ε–α with a = 1 – 2α ≲ 1, produced by Fermi acceleration or diffusive shock acceleration at multiple shocks combined with a synchrotron pile up. This basic mechanism is also plausible for flat-spectrum AGN.

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Gritsyk, P. A., and B. V. Somov. "Electron Acceleration in Collapsing Magnetic Traps during the Solar Flare on July 19, 2012: Observations and Models." Proceedings of the International Astronomical Union 13, S335 (July 2017): 90–93. http://dx.doi.org/10.1017/s1743921317008912.

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AbstractUsing the appropriate kinetic equation, we considered the problem of propagation of accelerated electrons into the solar corona and chromosphere. Its analytical solution was used for modelling the M7.7 class limb flare occurred on July 19, 2012. Coronal above-the-loop-top hard X-Ray source was interpreted in the thin-target approximation, the foot-point source - in the thick-target approximation with account of the reverse-current electric field. For the foot-point source we found a good accordance with the RHESSI observations. For the coronal source we also got very accurate estimate of the power-law spectral index, but significant differences between the modelled and observed hard X-ray intensities were noticed. The last discrepancy was solved by adding the coronal magnetic trap model to the thin target model. The former one implies that the trap collapses in two dimensions, locks and accelerates particles inside itself. In our report, we confirm an existence and high efficiency of the electron acceleration in collapsing magnetic traps during solar flares. Our new results represent (e.g. for RHESSI observations) the theoretical prediction of the double step particle acceleration in solar flares, when the first step is the acceleration in reconnection area and the second one – the acceleration in coronal trap.

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Li, Shao Hua, Chun Sheng Jiang, and Jin Yi Wu. "Structural Optimization of a Heavy-Duty Truck Based on a Virtual Prototype Model." Applied Mechanics and Materials 253-255 (December 2012): 2121–24. http://dx.doi.org/10.4028/www.scientific.net/amm.253-255.2121.

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A virtual prototype whole-body model was built for a tri-axial heavy-duty truck. Selecting the lateral acceleration, roll angle and yaw rate as the evaluation index, the sensitivity of wheelbase and track was analyzed and the coordinates of hard points were optimized. The Hunting behaviors of the optimized vehicle were discussed and compared with that of the original vehicle. It is shown that the roll angle, yaw rate and vertical acceleration of vehicle body and the vertical acceleration at the seat are reduced greatly after optimization. Thus the vehicle structural optimization improves both handling stability and ride comfort.

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Petrosian, Vahe’. "Non-Thermal Activity and Particle Acceleration in Clusters of Galaxies." Highlights of Astronomy 13 (2005): 317–21. http://dx.doi.org/10.1017/s1539299600015872.

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AbstractEvidence for non-thermal activity in clusters of galaxies is well established from radio observations of synchrotron emission by relativistic electrons, and new windows (in EUV and Hard X-ray ranges) have provided more powerful tools for its investigation. The hard X-ray observations, notably from Coma, are summarized and results of a new RXTE observations of a high red-shift cluster are presented. It is shown that the most likely emission mechanism for these radiations is the inverse Compton scattering of the cosmic microwave background photons by the same electrons responsible for the radio radiation. Various scenarios for acceleration of the electrons are considered and it is shown that the most likely model is episodic acceleration by shocks or turbulence, presumably induced by merger activity, of high energy electrons injected into the inter-cluster medium by galaxies or active galactic nuclei.

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Han, Bao, Guan Xin, Jia Xin, and Liu Fan. "A Study on Maneuvering Obstacle Motion State Estimation for Intelligent Vehicle Using Adaptive Kalman Filter Based on Current Statistical Model." Mathematical Problems in Engineering 2015 (2015): 1–14. http://dx.doi.org/10.1155/2015/515787.

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The obstacle motion state estimation is an essential task in intelligent vehicle. The ASCL group has developed such a system that uses a radar and GPS/INS. When running on the road, the acceleration of the vehicle is always changing, so it is hard for constant velocity (CV) model and constant acceleration (CA) model to describe the motion state of the vehicle. This paper introduced Current Statistical (CS) model from military field, which uses the modified Rayleigh distribution to describe acceleration. The adaptive Kalman filter based on CS model was used to estimate the motion state of the target. We conducted simulation experiments and real vehicle tests, and the results showed that the estimation of position, velocity, and acceleration can be precise.

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Batchelor, David. "Another clue about particle acceleration in impulsive hard X-ray/microwave bursts." Astrophysical Journal Supplement Series 90 (February 1994): 697. http://dx.doi.org/10.1086/191892.

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Batchelor, David. "Another Clue About Particle Acceleration in Impulsive Hard X-Ray/Microwave Bursts." International Astronomical Union Colloquium 142 (1994): 697–700. http://dx.doi.org/10.1017/s0252921100077988.

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AbstractIn a sample of impulsive bursts with rise times less than 30 s, a correlation between burst rise times and the frequency of maximum microwave emission has been found. The implications for source structure and dynamics are discussed in this paper. Previously evidence was found that such bursts are caused by some propagating disturbance such as a shock wave or thermal conduction front. Combining that evidence with the microwave and hard X-ray spectral information suggests that the most rapid bursts are emitted from the most compact and intensely magnetized sources. The most rapid bursts also exhibited the hardest X-ray spectra, as published previously. These facts are important clues to understanding the physical process responsible for impulsive bursts. A model for the bursts is suggested, based on the observations and inferences described.Subject headings: acceleration of particles — Sun: radio radiation — X-rays: bursts

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Gordevskyy, V. D. "Rotating flows with acceleration and compaction in the model of hard spheres." Theoretical and Mathematical Physics 161, no. 2 (November 2009): 1558–66. http://dx.doi.org/10.1007/s11232-009-0142-z.

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Benz, A. O., and S. R. Kane. "Electron acceleration in flares inferred from radio and hard X-ray emissions." Solar Physics 104, no. 1 (March 1986): 179–85. http://dx.doi.org/10.1007/bf00159960.

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Ren, Fu Shen, Ruo Xu Ma, and Xiao Ze Cheng. "Simulation of Particle Impact Drilling Nozzles Based on FLUENT." Advanced Materials Research 988 (July 2014): 475–78. http://dx.doi.org/10.4028/www.scientific.net/amr.988.475.

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The purpose of particles impact drilling is to increase the rate of penetration when drilling extra-hard and strong-abrasive rocks, where supposed to be time-consuming and costly. Now the technology becomes the world’s most potential drilling technology for deep wells and ultra-deep well. The most important part of the drilling technology is the nozzle which accelerate the particles. The paper introduces the basic four types of the nozzles, and researches the acceleration effect of nozzles based on FLUENT. By concluding the simulation, put up a new structure of nozzle, and simulates the acceleration of the particle of different drilling fluid and particles inlet velocities, discusses how the length of accelerating cavity affect the acceleration.

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Sapienza, Vincenzo, Marco Miceli, Aya Bamba, Satoru Katsuda, Tsutomu Nagayoshi, Yukikatsu Terada, Fabrizio Bocchino, Salvatore Orlando, and Giovanni Peres. "A Spatially Resolved Study of Hard X-Ray Emission in Kepler’s Supernova Remnant: Indications of Different Regimes of Particle Acceleration." Astrophysical Journal 935, no. 2 (August 1, 2022): 152. http://dx.doi.org/10.3847/1538-4357/ac8160.

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Abstract Synchrotron X-ray emission in young supernova remnants (SNRs) is a powerful diagnostic tool to study the population of high-energy electrons accelerated at the shock front and the acceleration process. We performed a spatially resolved spectral analysis of NuSTAR and XMM-Newton observations of the young Kepler’s SNR, aiming to study in detail its nonthermal emission in hard X-rays. We selected a set of regions all around the rim of the shell and extracted the corresponding spectra. The spectra were analyzed by adopting a model of synchrotron radiation in the loss-limited regime, to constrain the dependence of the cutoff energy of the synchrotron radiation on the shock velocity. We identify two different regimes of particle acceleration, characterized by different Bohm factors. In the north, where the shock interacts with a dense circumstellar medium (CSM), we found a more efficient acceleration than in the south, where the shock velocity is higher and there are no signs of shock interaction with the dense CSM. Our results suggest an enhanced efficiency of the acceleration process in regions where the shock–CSM interaction generates an amplified and turbulent magnetic field. By combining hard X-ray spectra with radio and γ-ray observations of Kepler’s SNR, we modeled the spectral energy distribution. In the light of our results we propose that the observed γ-ray emission is mainly hadronic and originates in the northern part of the shell.

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Campbell, K. W. "The Whittier Narrows, California Earthquake of October 1, 1987—Preliminary Analysis of Peak Horizontal Acceleration." Earthquake Spectra 4, no. 1 (February 1988): 115–37. http://dx.doi.org/10.1193/1.1585468.

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The Ml=5.9 Whittier Narrows, California, earthquake triggered several hundred accelerographs in the greater Los Angeles area. One-hundred and sixty-eight of these were used to develop attenuation relationships for peak horizontal acceleration. The analysis indicates that the attenuation of peak acceleration during the earthquake was generally consistent with that predicted from the attenuation relationships of Campbell (in press). However, the acceleration amplitudes were about 65-percent higher than predicted. An analysis of residuals clearly showed that the ground motions recorded during this earthquake were influenced by a complex interaction of source mechanism, building embedment, site geology, and geography. Source effects may have been responsible for the higher-than-expected accelerations as well as some of the observed azimuthal variation. The correlation of peak acceleration with geography may have been caused in part by the gross geologic structure of the region. Buildings with basements were observed to have lower accelerations than ground-level sites, consistent with previous results. Accelerations from rock sites—especially those from hard rock sites—were found to have lower amplitudes and greater variability than those from soil sites. The larger variability may be due in part to topographic effects. All sites located within about 20 km of the fault recorded about the same level of acceleration whether they were sited on deep soil, soft rock, or hard rock. Shallow-soil sites, however, had higher-than-average accelerations at relatively short distances, but lower-than-average accelerations at longer distances. Their behavior at long distances was more consistent with that of the underlying rock rather than that of the overlying soil, no doubt reflecting the longer wavelengths of the more distant ground motions.

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Wang, Xi, Hui Yu, and Wei Wu Zhong. "Acoustic Emission and Vibration Analysis of Process of Hard Dry Milling." Advanced Materials Research 97-101 (March 2010): 1915–19. http://dx.doi.org/10.4028/www.scientific.net/amr.97-101.1915.

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The monitoring of hard dry milling process is a key issue for ensuring better use of machine-tool capability,Finding a appropriate sensor and signal process method which is sensitive to changes of machining condition,is an essential step towards hard milling automation and computer-integration pursuing high productivity of system and quality of its products. In this study,Sensorial information from relevant sensors(accelerometer and Acoustic emission (AE))is processed by the wavelet transform and wavelet package transform,the result show that AE signal is sensitive to changes of machining parameter(machining velocity) in hard dry milling,but the vibration (acceleration) signal make a slowness responses to this .

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Aschwanden, Markus J., Arnold O. Benz, Brian R. Dennis, and Mukul R. Kundu. "Pulsed Acceleration in Solar Flares." International Astronomical Union Colloquium 142 (1994): 631–38. http://dx.doi.org/10.1017/s0252921100077903.

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AbstractWe study the nonlinear dynamics of particle acceleration in solar flares by analyzing the time series of various quasi-periodic radio signatures during flares. In particular we present the radio and hard X-ray data of three flares which support the following tentative conclusions:1.Particle acceleration and injection into magnetic structures occurs intrinsically in a pulsed mode (with a typical period of 1-2 s), produced by a single, spatially coherent, nonlinear system, rather than by a stochastic system with many spatially independent components (“statistical flare” produced by a fragmented primary energy release).2.The nonlinear (quasi-periodic) mode of pulsed particle acceleration and injection into a coronal loop can be stabilized by phase locking with an MHD wave (oscillation) mode, if both periods are close to each other.3.Pulsed injection of electron beams into a coronal loop may trigger nonlinear relaxational oscillations of wave-particle interactions. This is particularly likely when the limit cycles of both systems are similar.Subject headings: acceleration of particles— Sun: corona — Sun: flares — Sun: radio radiation — Sun: X-rays, gamma rays

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He, Yi, and Duan Feng Chu. "Evaluation and Modeling of Passenger Vehicle Celeration Performance Based on Artificial Neural Networks." Applied Mechanics and Materials 744-746 (March 2015): 1938–42. http://dx.doi.org/10.4028/www.scientific.net/amm.744-746.1938.

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As the siginificant factors influence passengers comfort, the vehicle celebration performance may easy to cause accidents, such as hard acceleration and deceleration performance. In order to find the relationship between passengers comfort and celebration performance, 35 passengers and three professional drivers were recruited in the field experiment. The passengers’ comfort feelings were analysed by subject questionnaires, the acceleration and deceleration data were received by CAN bus.The Artificial Neural Networks (ANNs) model was elaborated to estimate and predict the passengers comfort level of driver unsafe acceleration behavior situations. Therefore, the subject views of the passengers could be compared to object acceleration data. An ANN is applied to interconnect output data (subjective rating) with input data (objective parameters). Finally, it is found the investigatioin have demonstrated that the objective values are efficiently correlated with the subjective sensation. Thus, the presented approach can be effectively applied to support the drive train development of bus.

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Anwar Abdullah, Mayson. "Acceleration of the Calcium Carbonate Precipitation in Hard Water by using Electrolysis Process." Journal of Engineering and Applied Sciences 14, no. 19 (October 31, 2019): 7089–92. http://dx.doi.org/10.36478/jeasci.2019.7089.7092.

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YAMAURA, Hiroshi, Kyosuke ONO, and Makoto NISHIMURA. "Vibrationless acceleration control of positioning mechanisms and its application to hard-disk drives." Transactions of the Japan Society of Mechanical Engineers Series C 56, no. 522 (1990): 344–50. http://dx.doi.org/10.1299/kikaic.56.344.

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Kong, Chunyan, Rongjun Zhu, Derong Zhang, and Shuangshuang Li. "Research on kinematics analysis of spherical single-cone PDC compound bit and rock breaking simulation verification." Oil & Gas Science and Technology – Revue d’IFP Energies nouvelles 76 (2021): 52. http://dx.doi.org/10.2516/ogst/2021034.

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The single-cone bit has become the first choice for slim hole sidetracking and deep well drilling with its unique rock breaking method and high ROP (Rate Of Penetration), with its main failure mode being of early excessive wear of the cutting teeth. In order to improve the adaptability of single-cone bits to hard and highly abrasive formations, a spherical single-cone Polycrystalline Diamond Compact (PDC) compound bit is designed. According to the characteristics of the tooth profile, the way of tooth arrangement and the way of contact between the cutting teeth and the rock, the acceleration equation to the cutting teeth of the spherical single-cone PDC compound bit is established. The acceleration of the single-cone bit is verified by numerical simulation experiment of rock-breaking. The shaft inclination angle of the cone, the position and height of the PDC teeth, the radius of the PDC teeth, the lateral rotation angle and the front inclination angle on the acceleration are studied. The results show that as the shaft inclination angle increases, the bit transmission ratio gradually increases, and the harder the rock formation, the larger the transmission ratio of the single-cone bit; the shaft inclination angle and the position of the PDC tooth have a greater influence on the acceleration of the PDC tooth, and the radius, lateral rotation angle and front inclination angle of the PDC tooth have a small influence on the acceleration of the PDC tooth; rock properties have an impact on the acceleration of the cutting teeth, with the acceleration of the cutting teeth in hard rock formations being higher than that in soft rock formations; near the top of the cone, the absolute acceleration of the cutting teeth will fluctuate sharply and cause severe wear of the cutting teeth, so the tooth distribution in this area should be strengthened; on the premise that the bearing life of the single-cone bit is allowed, the value of the shaft inclination angle β can be approached to 70°. The relative error between the theoretical analysis results of the acceleration of the PDC cutter and the rock-breaking simulation experiment results is between −0.95% and −2.24%. This research lays a theoretical foundation for the dynamic research of spherical single-cone PDC compound bit.

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Panda, Amlana, Ashok Kumar Sahoo, Isham Panigrahi, and Arun Kumar Rout. "Prediction models for on-line cutting tool and machined surface condition monitoring during hard turning considering vibration signal." Mechanics & Industry 21, no. 5 (2020): 520. http://dx.doi.org/10.1051/meca/2020067.

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Turning of hardened steel is an immense issue of interest concerning with machining technology and scientific research. A strategy to analyze vibration signals and its correlation on surface roughness and tool wear has not attracted much breakthrough in research so far in hard machining. Therefore, tool condition monitoring (TCM) study will be definitely worthwhile for the effective application in hard part turning. The current study examines about the online prediction of flank wear and surface roughness monitoring during dry hard turning of AISI 52100 steel (55 ± 1 HRC) utilizing MTCVD multilayer coated carbide insert (TiN/TiCN/Al2O3) considering machining parameters and vibration signals through development of prediction model (MLR and MQR) after studying the Pearson correlation coefficient and test for its accuracy. Pearson correlation coefficient for feed on flank wear is utmost pursued by acceleration amplitude of vibration (Vy) in radial direction, depth of cut and cutting speed. Similarly, acceleration amplitude of vibration followed by cutting speed and feed has strong correlation with surface roughness. MQR model predicts well for responses as percentage of error is quite less and cutting speed is obtained to be the most important parameter for vibration signal. Multiple quadratic regression (MQR) models are observed to be noteworthy, effective and adequate to predict response outputs with regards to the combined effect of machining parameters and vibration signals online. A corrective measure can safely be taken with reasonable degree of accuracy during hard turning.

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Safi-Harb, Samar, Brydyn Mac Intyre, Shuo Zhang, Isaac Pope, Shuhan Zhang, Nathan Saffold, Kaya Mori, et al. "Hard X-Ray Emission from the Eastern Jet of SS 433 Powering the W50 “Manatee” Nebula: Evidence for Particle Reacceleration." Astrophysical Journal 935, no. 2 (August 1, 2022): 163. http://dx.doi.org/10.3847/1538-4357/ac7c05.

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Abstract We present a broadband X-ray study of W50 (the “Manatee” nebula), the complex region powered by the microquasar SS 433, that provides a test bed for several important astrophysical processes. The W50 nebula, a Galactic PeVatron candidate, is classified as a supernova remnant but has an unusual double-lobed morphology likely associated with the jets from SS 433. Using NuSTAR, XMM-Newton, and Chandra observations of the inner eastern lobe of W50, we have detected hard nonthermal X-ray emission up to ∼30 keV, originating from a few-arcminute-sized knotty region (“Head”) located ≲18′ (29 pc for a distance of 5.5 kpc) east of SS 433, and constrained its photon index to 1.58 ± 0.05 (0.5–30 keV band). The index gradually steepens eastward out to the radio “ear” where thermal soft X-ray emission with a temperature kT ∼ 0.2 keV dominates. The hard X-ray knots mark the location of acceleration sites within the jet and require an equipartition magnetic field of the order of ≳12 μG. The unusually hard spectral index from the “Head” region challenges classical particle acceleration processes and points to particle injection and reacceleration in the subrelativistic SS 433 jet, as seen in blazars and pulsar wind nebulae.

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Vilmer, N. "Solar Hard X-Ray and Gamma-Ray Observations from GRANAT." International Astronomical Union Colloquium 142 (1994): 611–21. http://dx.doi.org/10.1017/s0252921100077885.

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AbstractHard X-rays and gamma-rays are the most direct signature of the energetic electrons and ions which are accelerated during solar flares. Since the beginning of 1990 the PHEBUS instrument and the SIGMA anticoincidence shield aboard GRANAT have provided hard X-ray and gamma-ray observations of solar bursts in the energy range 0.075-124 and 0.200-15 MeV, respectively. After a brief description of the experiments, we present some results obtained on solar bursts recorded in 1990 and 1991 June. Special emphasis is given to the results related with particle acceleration during solar flares.The first part of the review is devoted to the constraints obtained on the electron acceleration timescale through the analysis of the temporal characteristics of the bursts. Combined studies of hard X-ray and gamma-ray emissions from PHEBUS and radio emissions from the Nançay Multifrequency Radioheliograph are used to infer constraints on the coronal magnetic topology involved in flares. The characteristics (location, spectrum) of the radio-emitting sources are found to vary within a flare from one hard X-ray peak to the other. Hard X-ray and gamma-ray burst onsets and rapid increases of the > 10 MeV emission are coincident with changes in the associated radio emission pattern. These results will be discussed in the context of the flare energy release.The second part of the paper concerns the heliocentric angle distribution of > 10 MeV events and presents more detailed observations of some of the largest flares in the gamma-ray line and the high-energy domains produced by ultrarelativistic electrons and > 100 MeV nucleon−1 ions. The PHEBUS observations of the gamma-ray line flare of 11 June 1991 have been used to deduce the hardness of the accelerated ion spectrum. The link between the main part of the flare and the late long-lasting >50 MeV emission detected by EGRET/COMPTON is discussed. Finally some observations of the large 1990 May 24 flare which produced a large neutron event at ground level are presented.Subject headings: acceleration of particles — Sun: flares — Sun: radio radiation — Sun: X-rays, gamma rays

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SIGURDSSON, STEINN. "TESTING GRAVITY IN LARGE EXTRA DIMENSIONS USING BOSE–EINSTEIN CONDENSATES." International Journal of Modern Physics D 11, no. 10 (December 2002): 1541–44. http://dx.doi.org/10.1142/s0218271802002864.

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Recent conjectures that there are mesoscopically "large" extra dimensions, through which gravity propagates have interesting implications for much of physics. The scenario implies gross departures from Newton's law of gravity at small length scales. Testing departures from Coulomb's law on sub-millimetre scales is hard. It is now possible to routinely create Bose–Einstein condensates with de Broglie wavelengths of order a μm and total size of order 10 μm. BEC condensates move coherently under gravitational acceleration, and I propose that the transverse fringe shift due to the acceleration of a pair of interfering BECs passing a dense linear mass may be measurable, and provide direct evidence for anomalous gravitational acceleration. Ideally such experiments are best carried out in free fall to maximise the time spent by a BEC in the non-Newtonian regime.

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Sunardi, Bambang, Sulastri, Dwikorita Karnawati, Urip Haryoko, Supriyanto Rohadi, Sigit Pramono, and Ari Sungkowo. "Acceleration Response Spectra for M 7.4 Donggala Earthquake and Comparison with Design Spectra." Journal of Sustainable Engineering: Proceedings Series 1, no. 1 (June 30, 2019): 20–26. http://dx.doi.org/10.35793/joseps.v1i1.3.

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A 7.4 magnitude earthquake have strucked Donggala on September 28th 2018, followed by tsunami and liquefaction which hit Palu, Central Sulawesi, a few minutes later. This event had resulted in damage to buildings, and caused more than 2,000 people were killed and injured. Indonesia already have a building code in form of SNI 1726:2002 which had been updated to SNI 1726:2012. This paper analyses the hazard level caused by the 2018 Donggala earthquake compared to the existing design spectra, as mentioned in SNI 1726:2002 and SNI 1726:2012. A simple analysis was carried out by comparing Donggala earthquake’s acceleration response spectra with the existing design spectra, at the MPSI accelerograph station. The site class at MPSI station is hard soil (SC). The seismic hazard in Palu and Donggala refers to SNI 1726:2002 is included in the earthquake area 4. The maximum earthquake response factor for earthquake area 4 is about 0.6 for hard soil type (SC). The MPSI station recorded peak ground acceleration of Donggala earthquake around 0.14 g. The acceleration response spectra recorded at the MPSI station showed a peak value of around 0.71 g for the N component. This value is actually still below the design spectra referring to SNI 1726:2012, which the peak value is 0.88 g for SC, but, it exceeded the design spectra of SNI 1726:2002.

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Partono, Windu, Masyhur Irsyam, Indrastono Dwi Atmanto, Andi Retno Ari Setiaji, Sigit Purnomo, and Robby Yanuar Setiawan. "Building evaluation using two components of acceleration time histories causes by shallow crustal fault earthquakes with maximum magnitude 7 Mw." MATEC Web of Conferences 195 (2018): 02011. http://dx.doi.org/10.1051/matecconf/201819502011.

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Spectral acceleration and acceleration time histories are the two seismic loads generally used for dynamic analysis of a building. The structural design of buildings is implemented using spectral acceleration at the ground surface obtained from the national seismic code. However, acceleration time histories are developed from specific earthquake events and implemented for building evaluation. This paper presents building evaluations of three existing buildings located in Semarang with heights of at least 40 m. The buildings were built on three different soil types, that is, hard, medium and soft soils. The evaluation was performed by conducting two component north-south and east-west directions of acceleration time histories modified from Semarang fault earthquake scenarios having a magnitude of 7 Mw and maximum epicentre distance 15 Km. Due to incomplete data on Semarang fault earthquakes, the acceleration time histories incorporated herein were collected from worldwide earthquake data bases and modified using response spectral matching and seismic propagation analysis. Stability analyses in terms of structural deformation and drift ratio were carried out for the three buildings. The results show that all three buildings have the capability to resists earthquakes up to a maximum magnitude of 6.5 Mw with an epicentre distance of over 5 Km.

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Ambhore, Nitin, Dinesh Kamble, and Satish Chinchanikar. "Analysis of tool vibration and surface roughness with tool wear progression in hard turning: An experimental and statistical approach." Journal of Mechanical Engineering and Sciences 14, no. 1 (March 23, 2020): 6461–72. http://dx.doi.org/10.15282/jmes.14.1.2020.21.0506.

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The machined surface quality and dimensional accuracy obtained during hard turning is prominently gets affected due to tool wear and cutting tool vibrations. With this view, the results of tool wear progression on surface quality and acceleration amplitude is presented while machining AISI 52100 hard steel. Central Composite Rotatable Design (CCRD) is employed to develop experimental plan. The results reported that vibration signals sensed in a tangential direction (Vz) are most sensitive and found higher than the vibrations in the feed direction (Vx) and depth of cut direction (Vy). The acceleration signals in all three directions are observed to increase with the advancement of tool wear and good surface finish is observed as tool wear progresses up-to 0.136mm. The vibration amplitude is discovered high in the range 3 kHz – 10 kHz within selected cutting parameter range (cutting speed 60-180mm/min, feed 0.1-0.5mm/rev, depth of cut 0.1-0.5mm). The investigation is extended for the development of multiple regression models with regression coefficients value 0.9. These models found statically significant and give dependable estimates between a tool vibrations and cutting parameters.

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Uneda, Michio, Keiichi Takano, Koji Koyama, Hideo Aida, and Ken-ichi Ishikawa. "Investigation into Chemical Mechanical Polishing Mechanism of Hard-to-Process Materials Using a Commercially Available Single-Sided Polisher." International Journal of Automation Technology 9, no. 5 (September 5, 2015): 573–79. http://dx.doi.org/10.20965/ijat.2015.p0573.

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Chemical mechanical polishing (CMP) is one of the most important processes for fabricating highly planarized substrates such as sapphire for light emitting diodes (LEDs). However, sapphire is categorized as a hard-to-process material; therefore, a long processing time is required because of the low polishing efficiency (i.e., removal rate). This study investigates the CMP mechanism for hard-to-process materials using the following polishing evaluation parameters: (1) the velocity ratio, which is defined as the ratio of slurry flow velocity between the wafer and polishing pad during CMP to the pad tangential velocity, (2) the standard deviation of the velocity ratio distribution, and (3) the polisher vibration acceleration during CMP. Each parameter was measured at five rotational speeds and two polishing pressures for a total of ten conditions using a commercially available single-sided polisher. Moreover, the influence of each parameter on the removal rate was demonstrated via a multiple correlation analysis. As a result, we revealed that the velocity ratio and polisher vibration acceleration are strongly related with the removal rate.

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Aschwanden, M. J., L. Fletcher, T. Sakao, T. Kosugi, and H. Hudson. "Electron Trapping and Precipitation in Asymmetric Solar Flare Loops." Symposium - International Astronomical Union 195 (2000): 375–76. http://dx.doi.org/10.1017/s0074180900163168.

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Acceleration, propagation, and energy loss of particles energized in solar flares cannot be studied separately because their radiative signatures observed in the form of hard X-ray bremsstrahlung or radio gyrosynchrotron emission represent a convolution of all these processes. We analyze hard X-ray emission from solar flares using a kinematic model that includes free-streaming electrons (having an energy-dependent time-of-flight delay) as well as temporarily trapped electrons (which are pitch-angle scattered by Coulomb collisional scattering) to determine various physical parameters (trapping times, flux asymmetry, loss-cone angles, magnetic mirror ratios) in flare loops with asymmetric magnetic fields.

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Tanaka, Shuta J. "On the Radio Emitting Particles of the Crab Nebula: Stochastic Acceleration Model." Proceedings of the International Astronomical Union 13, S337 (September 2017): 259–62. http://dx.doi.org/10.1017/s1743921317008754.

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AbstractThe standard shock acceleration model of pulsar wind nebulae (PWNe) does not account for the hard spectrum in radio wavelengths. The origin of the radio-emitting particles is also important to determine the pair production efficiency in the pulsar magnetosphere. Here, we propose a possible resolution for the particle energy distribution in PWNe; the radio-emitting particles are not accelerated at the pulsar wind termination shock but are stochastically accelerated by turbulence inside PWNe. We upgrade our past one-zone spectral evolution model including the energy diffusion, i.e., the stochastic acceleration, and apply to the Crab Nebula. For a particle injection to the stochastic acceleration process, we consider the continuous injection from the supernova ejecta or the impulsive injection associated with supernova explosion. The observed broadband spectrum and the decay of the radio flux are reproduced by tuning the amount of the particle injected to the stochastic acceleration process. Our results imply that some unveiled mechanisms, such as back reaction to the turbulence, are required to make the energies of stochastically and shock accelerated particles comparable.

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Charikov, Yu E., E. M. Sklyarova, and A. N. Shabalin. "Subsecond Hard X-Ray Spikes from Solar Flares: Limitations on the Electron Acceleration Mechanism." Geomagnetism and Aeronomy 61, no. 8 (December 2021): 1093–100. http://dx.doi.org/10.1134/s001679322108003x.

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Xu, Siyao, and Bing Zhang. "Adiabatic Non-resonant Acceleration in Magnetic Turbulence and Hard Spectra of Gamma-Ray Bursts." Astrophysical Journal 846, no. 2 (September 8, 2017): L28. http://dx.doi.org/10.3847/2041-8213/aa88b1.

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NAKAMURA, Sumiko, and Ken’ichi OHTSUBO. "Acceleration of Germination of Super-Hard Rice Cultivar EM10 by Soaking with Red Onion." Bioscience, Biotechnology, and Biochemistry 75, no. 3 (March 23, 2011): 572–74. http://dx.doi.org/10.1271/bbb.100621.

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Kalinin, Ya V. "ON THE CONSTRUCTION OF ENERGY-EFFICIENT ALGORTIMS OF THE WALKING ROBOT RAISING AND BRAKING." IZVESTIA VOLGOGRAD STATE TECHNICAL UNIVERSITY, no. 9(244) (September 25, 2020): 44–48. http://dx.doi.org/10.35211/1990-5297-2020-9-244-44-48.

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An energetically effective motion of a walking robot on a hard ground is considered. With the help of the methods of the classical calculus of variations, laws of the optimal acceleration and deceleration energy of the robot are calculated based on the minimum criterion. The resulting motion laws correspond to the extremals of the investigated quality functional.

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Tanaka, Motohiko, and K. Papadopoulos. "Creation of High-Energy Electron Tails by the Lower-Hybrid Waves and its Relevance to Type II and III Bursts." Symposium - International Astronomical Union 107 (1985): 505–8. http://dx.doi.org/10.1017/s0074180900076026.

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It is commonly anticipated that high-energy electrons play an important role for the wave emission in flare bursts. For instance, electrons with >100 KeV are considered to create microwave emissions through gyro-synchrotron process and hard x-rays may be due to bremstrahlung with >25 KeV electrons. However, electron acceleration mechanism itself is still in speculations.

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Rovelli, Antonio, Shri K. Singh, Luca Malagnini, Alessandro Amato, and Massimo Cocco. "Feasibility of the use of Microtremors in Estimating Site Response during Earthquakes: Some Test Cases in Italy." Earthquake Spectra 7, no. 4 (November 1991): 551–61. http://dx.doi.org/10.1193/1.1585643.

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We explore the feasibility of the use of microtremors in estimating the amplification of seismic waves at soft sites in Italy. Microtremors were measured at three soft sites and nearby hard sites at night when the cultural noise was minimum. These soft sites were selected as those showing the largest amplifications of ground motion during earthquakes as compared to the records on the hard sites or with respect to the predicted spectra. We compare the soft-to-hard site microtremor spectral ratios with the corresponding acceleration spectral ratios. A rough estimate of the shape and level of spectral amplification is obtained from the microtremor data in all three cases. However, the details of the soft-to-hard site spectral ratio are not reproduced and some differences appear in (a) the frequency at which the maximum amplification occurs, and (b) the bandwidth of the significant amplification. More testing of the method is needed before its wider use for microzonation in Italy can be recommended.

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Journal articles on the topic 'Hard-acceleration'

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